TCP performance over heterogeneous networks

In future IP networks, nodes supporting new congestion avoidance mechanisms like RED and ECN are going to exist together with nodes carrying traditional drop tail buffers. We study the performance of a set of TCP flows passing through two congested nodes in such a heterogeneous network. Our results show that unequal hop behaviour (in the form of RED and drop tail) in the congestion points can increase the bias against TCP flows passing through multiple congested nodes. Parameter settings of RED become critical again in the dual-bottleneck situation just like in the single-bottleneck case. Furthermore, appropriate settings for single- and dual-bottleneck situations appear to be significantly different, making it more problematic for RED to provide a “better-than-drop tail” performance with a fixed set of parameters